Prevalence and Geographic Distribution Pattern of Asthma in Tehran by ECRHS.

Background: Asthma, involving 5–10% of global population, has a heterogeneous distribution in the community regardless of age and its prevalence and incidence tend to grow worldwide as reported by many recent epidemiologic surveys. Materials and Methods: The present study aimed to survey the prevalence of asthma symptoms in Tehran as the first attempt in terms of situation analysis of the disease in the Iranian society by using relevant parts of the European Community Respiratory Health Survey (ECRHS) questionnaire. Results: Wheezing was reported in 48% of males and 34% of females in the age range of 20–44 years, around 50% of which was associated with breathlessness or cold., the people who answered “yes” to the questions 1 (wheezing), 4 (coughing), 5 (asthma history) or 7 (nasal allergy) were totally 211 among whom 124 (58.8%) were males and the rest (41.2%) were females. Conclusion: Asthma symptoms decrease the quality of life and impose high costs on the healthcare system in many countries. A low rate of participants had been informed about their asthma by physicians and not all of them were taking medications. Risk factor analysis and control is strongly advised in order to lessen the prevalence of the disease and symptoms. Air pollution, smoking, unhealthy life style and many personal and social factors need to be assessed and eliminated. It seems that a- second phase- ECRH survey should be conducted to assess the situation of asthma through population of Tehran.


INTRODUCTION
Bronchial asthma is known as a complex chronic inflammatory disease which is usually characterized by reversible airway obstruction and hyper-reactivity. Asthma is often diagnosed with symptoms such as wheezing, nocturnal or early morning cough, and shortness of breath by physicians in community setting (1)(2)(3)(4)(5)(6). This disease has a heterogeneous distribution in the community irrespective of age and its prevalence and incidence tend to grow worldwide as reported by many recent epidemiologic surveys (1,7). The incidence of asthma cannot be determined precisely, mainly due to the lack of a general gold standard for asthma definition and causes (6,8). An observable growth in asthma prevalence in the recent years has been a strong motivation to start comprehensive global studies in this regard (9,10). This rapidly increased prevalence is not caused by a single factor like genetics, age, or air pollution. Thus, many factors are to be evaluated in this disease (11). A trend study in Italy by de Marco and colleagues shows a growing prevalence of TANAFFOS asthma and allergic rhinitis as well as asthma-like symptoms from 1991 to 2010 and the authors point to a 38% increase in asthma prevalence during 20 years (12). Sigurkarlsson et al. shows three-fold increase in the prevalence of asthma attacks and use of anti-asthmatic drugs between 1990 and 2007 in the young population (13). This condition has created a significant burden on the healthcare system due to increased morbidities and reduced quality of life (14,15 (17), among which the latter was successfully followed by the present study. The ECRHS was the first study to assess the situation of asthma in adults in 25 countries in three phases evaluating geographical prevalence, risk factors, treatment and follow up of asthma (9,17,18). The questionnaire used in ECRHS is now one of the most popular instruments for epidemiologic studies due to its validity and acceptability.

Similar attempts in Iceland by
It contains 10 simple and specific questions used perfectly in large-scale surveys on asthma (1,19) although the subjective character of the questionnaire limits the accuracy of asthma detection and may overestimate the prevalence of the disease (20). However, the ECRHS questionnaire has been the most perfect tool to obtain data in this matter so far, which could be used in the Middle East where the data regarding asthma prevalence are scarce (1).
There have been other studies working on asthma in children. To our knowledge, no population-based study has explored the prevalence of adult asthma in Tehran.
Accordingly, the present study aimed to assess the prevalence of asthma in Tehran as the first attempt in situation analysis of the disease in an Iranian society by using relevant parts of the ECRHS questionnaire.

MATERIALS AND METHODS
Population and sampling strategy: The study was done through a cross-sectional design to assess the frequency of asthma and wheezing in Tehran with 8.1 million population. We used stratified cluster sampling considering urban regions and the density of population all over the city.
Sample Size: To obtain a study power of at least 80% in addition to the effect size of l.5, and a response rate of 60%, the sample size was calculated to be 961 participants to answer "yes" to the questions 3, 5 or 6 of ECRHS questionnaire. We needed to enroll 3,366 people to obtain accurate results.
Sampling: As pointed out before, the design for sampling was a stratified cluster strategy using This number was also affected by the total sample size, mean number of household members, and logistical facilities for subject enumeration, transport, and examination. There were three-member teams to refer the clusters in order to obtain data. Two interviewers, a man and a woman dressed in white medical coats, in addition to a driver were recruited. The interviewing team approached the index household specified via a random selection of clusters, and continued the enumeration in 10 neighboring households in a systematic manner by proceeding in a clock-wise direction. The interviewers were advised to try the Kish Grid or method to choose the right participant(s) when there was more than one person in the indexed household. The named method is simply a table of numbers which is used to find the number of residents in the household. Then, a randomly selected number would determine the person who is the one to recruit.
Definition: Asthma is a chronic inflammatory disorder associated with variable airflow obstruction and bronchial hyper-responsiveness. It presents with recurrent episodes of wheeze, cough, shortness of breath and chest tightness (6).

Examination Protocol: A comprehensive ECRHS
questionnaire was used through a broad survey and the present study was part of it. All questionnaires were filled out by interviewers. Respiratory symptoms, health status, activity limitation, and risk factor exposure were the items to assess among which symptoms and signs of asthma, especially wheezing in addition to relevant medical history were the most focused ones. The core questionnaire was developed using preexisting validated questionnaire that had already been used in multinational studies.
Statistical Analysis: The present study used SPSS 21 for windows to gather the data and analyze them considering the 95% confidence interval while defining the significance <0.05 and type 1 error equal to 0.05. The frequencies were reported through central statistical tendency indices using t-test and chi-square test. More details in terms of the materials and methods of this study have already been published elsewhere (21).

RESULTS
Totally, 3,366 subjects enrolled the survey by answering the ECRHS questionnaire amongst them 1,755 (52.2%) were males and 1,611 (47.8%) females (Table 1). as can be seen in Figure 1.
In terms of breathlessness, both males and females showed a slow process in its occurrence as the age raised ( Figure 2).
The mean age was significantly different between males and females (P<0.001).
Based on the protocol of ECRHS, people between 20-44 years of age were included in the present study. Thus, as presented in Table 4, of 2,984 individuals 51% were males and 49% were females in the selected age range. Wheezing was reported in 48% of males and 34% of females around a half of which was with breathlessness or cold. Wheezing and the history of dyspnea were the significantly different items with regard to participants' gender.  Asthma affects 5-10% of the world's population.
Its severity is assessed by pulmonary function test, symptom frequencies and exacerbation rate as well as rescue inhaler use (24). It is mainly a childhood disease although it is too hard to know its precise definition and prevalence in adults (25 any other region in the world (1). They found no difference between the sexes in this matter, as also noted in our study.
Some researchers have even aimed to find genetic effects on the frequency and distribution of asthma symptoms and disease to find polymorphisms and probable mutations in some target genes (36).
In conclusion, asthma symptoms compromise the quality of life besides directing high costs on the healthcare system in many countries and would be too hard to control, especially in developing countries with limited health budget. Thus, risk factor analysis and control is strongly advised in order to lessen the prevalence of the disease and symptoms. Air pollution, smoking, imperfect life style and many personal and social factors need to be assessed and eliminated.